1. Field of the Invention
The present invention relates to a line-with measurement technology, especially to a line-width measurement device and a measurement method using the same that increase accuracy of line-width measurement.
2. Description of the Related Art
With the development of semiconductor manufacturing process, integrated circuit elements are progressively made much smaller. Therefore, in the semiconductor manufacturing process, control of critical dimension, such as line width, line pitch, etc. of fine circuit patterns on masks or wafers, is an important point. Generally, manufacturers use line-width measurement device to measure critical dimensions of circuit patterns, the line-width measurement device can be used to inspect if the line width or pitch is precise without deviation.
With reference to FIG. 1, FIG. 1 is a schematic view of performing line-width measurement according to a conventional technology. The conventional technology uses an image capturing device 91 (such as a CCD camera) to capture an image from a pattern 92 under measurement, and then performs line-width measurement through computer processing. The image capturing device is usually assembled together with a light source device 90. The light source device 90 provides illumination in a forward direction on a top of the pattern 92 under measurement, so that the image capturing device is able to capture a clear image.
The captured image is colored and will be converted into a gray scale image for the operation of line-width measurement. In general, before a computer performs line-width measurement of the gray scale image, it will first load an image of a standard pattern as a measuring reference. With reference to FIG. 2, lights from the light source device 90 in FIG. 1 will pass through a filter 93 to provide suitable illumination so that the gray scale image converted from the captured image can have similar color contrast with the standard pattern for performing line-width measurement. The filter 93 used in the light source device for line-width measurement generally includes five kinds of filter units 930 having different colors to provide different choices of colored illumination so that different gray scale images can be obtained by using the lights projected through the different filter units 930.
However, when the gray scale image of the pattern under measurement has a big difference in color contrast with the standard pattern, it will affect the accuracy of line-width measurement. Because foregoing filter 93 only provides five kinds of filter units 930, the light source device 90 can only provide five kinds of colored illumination. Since different patterns under measurement may be made of materials having different reflection characteristics, only five choices of colored illumination will have limited room to adjust the gray scale image of the pattern under measurement.
Therefore, it is necessary to provide a line-width measurement device and a measurement method using the same to overcome the problems existing in the conventional technology.